The present invention relates to such a ground excavating apparatus as is suitable for excavating the heterogeneous ground consisting of hard and soft stratums including a rock bed and gravel.
The excavating apparatuses so far designed and manufactured for the purpose of conducting building of a tunnel or excavation of the ground are multifarious and diversiform, and are roughly classified into those of the bucket type proving suitable for excavating the soft ground and those of the impact crusher type proving suitable for excavating the comparatively hard ground.
The bucket type is such a type that generally conducts excavation of the soft ground by the operation of a bucket fitted in place on the top section of a bucket boom, hence unsuitable at all for the excavation of the hard ground. Meanwhile, the impact crusher type, on the part thereof, is what is applied to building of a tunnel in an extensive manner, and this category of ground excavating apparatus is what is employed for conducting excavation by cutting and crushing the face is a continuous manner without employing gunpowder, unlike the case of a blasting process.
The tunnel excavators presently employed are roughly classified into those of the total section cutting system and those of the partial section cutting system. The tunnel excavators of the partial section cutting system are those hitherto employed for excavating a coal mine and specifically remodeled for the purpose of conducting excavation for building a tunnel. The tunnel excavator of the total section cutting system are generally those employed for conducting excavation to a circular section. Multifarious models of tunnel excavators of the impact crusher type have been developed thus far, and have such common characteristics that generally cause the cutter thereof to be revolved, and to be given proper impellant force as well, for the purpose of conducting proper cutting or crushing of a rock.
However, for all the fact that the said bucket type and the said impact crusher type prove to be effective and efficient enough, in case the ground is well stabilized with a soft stratum and a hard rock bed, respectively, excavation by the employment of only either one of the said types is still impracticable or inefficient in the case of a general excavation work, since therein exist a variety of stratums in a mixed form as a reality.